You can edit the diamonds compatible with each ring by updating the metafields on a product level.
By entering into the Products > Select Product > Scroll down > Add variant > Name the variant Diamond Shape > Add the shapes you would like to show for each ring.
You can also add media for the picture to change with each variant which can be seen on our demo store here.
Don’t forget to add each item into your stock to ensure they are showing as available on your store.
A list of all available shapes can be found below
"ASSCHER,BAGUETTE,BRIOLETTE,BULLET,CALF,CUSHION_ALL,CUSHION_BRILLIANT,CUSHION_MODIFIED,CUSHION,EMERALD,EUROPEAN_CUT,FLANDERS,HALF_MOON,HEART,HEXAGONAL,KITE,LOZENGE,MARQUISE,OCTAGONAL,OLD_MINER,OTHER,OVAL,PEAR,PENTAGONAL,PRINCESS,RADIANT,ROSE,ROUND,SHIELD,SQUARE_EMERALD,SQUARE_RADIANT,SQUARE,STAR,TAPERED_BAGUETTE,TAPERED_BULLET,TRAPEZOID,TRIANGULAR,TRILLIANT"